whats all of this id address mark stuff? [FDD]

earlz · Post by **earlz** » Sat Jul 15, 2006 2:06 pm

so what exactly is it, I'm reading this tutorial http://web.archive.org/web/200410100810 ... loppy.html
and it keeps referring to id address marks and track address marks, but what is it!?

chase · Post by **chase** » Mon Jul 17, 2006 3:44 am

Sounds like the hidden sector data. On hard drives and floppies sectors store 512 bytes of user data but in reality they are larger and store location and CRC type information as well. It probably should be created for you when you write a sector and an error about being unable to read address marks probably means your floppy needs formatting, is bad, or the drive has gone out.

chase · Post by **chase** » Mon Jul 17, 2006 9:23 am

Think I found what exactly the address mark is in a WDC floppy controller doc (http://saint.atari.org/html/doc/wd1772.html)

Read Sector:
The controller waits for a sector ID field that has the correct track
number, sector number, and CRC. The controller then checks for the
Data Address Mark, which consists of 43 copies of the second byte of
the CRC. If the controller does not find a sector with correct ID
field and address mark within 5 disk revolutions, the command ends.